Hydraulic oscillators



Jan. 24, 1956 H. E. B. scoT-r HYDRAULIC OSCILLATORS 5 Sheets-Sheet l Filed Dec. 22 1950 y; fk.. I i

Jan. 24, 1956 H. E. B. sco'r'r 2,731,953

HYDRAULIC OSCILLATORS Filed Dec. 22, 1950 5 Sheets-Sheet 2 Jan. 24, 1956 H. E. B. SCOTT HYDRAULIC OSCILLATORS 3 Sheets-Sheet 5 Filed Deo. 22 1950 .I'N vwrae Hamm Ir/c En m .53m

United States Patent O 2,731,953 HYDRAULIC osclLLAToRs Harold Eric Baliol Scott, Weybridge, England Application December 22, 1950, Serial No. 202,167 2 Claims. (Cl. 121-157) The object of this invention is to provide a reciprocating hydraulic motor for imparting to and fro movement to a member to be actuated. The motor according to the invention is eminently suitable for imparting reciprocating movement to a doctor associated with the rolls of a paper making machine and for actuatinga shower pipe.v Such uses are, however, illustrative only as the motor is of general utility.

One of the primary objects of this invention is to provide a reciprocating hydraulic motor having a reversing valve in which the valve actuation is hydraulic, is derived from the reciprocation of the motor, and is not dependent on-external or mechanical means such as cams, eccentrics, etc.

The hydraulic motor according to the invention comprises a casing having an inlet for liquid under pressure and an exhaust outlet, a pressure sensitive actuator mounted to reciprocate in the casing, a pilot valve in the casing, a sleeve valve surrounding the pilot valve and mounted for reciprocation thereon between two alternative controlling positions, said sleeve valve serving to establish a pressure difference acrossthe actuator which is reversed in direction as the sleeve valve moves from one controlling position to the other, and said pilot valve serving to establish a hydraulic pressure dierence across the sleeve valve, which is periodically reversed in direction,` by relative movement of the sleeve valve and pilot valve, to cause movement of the sleeve valve from one controlling position to the other, and said actuator being arranged, as it is reciprocated by reversal of the pressure difference across it, to impart the aforesaid relative movement to the sleeve valve and pilot valve.

The actuator, which will be coupled to the member to be actuated by the motor, may be constituted by a pair of pistons or diaphragms of unequal areawhich are coupled together, the outer face of the smaller piston or diaphragm being subject continuously to pressure and the outer face of the larger piston or diaphragm being subject alternately to pressure and exhaust according to the controlling position assumed by the sleeve valve. Alternatively, the pistons-or diaphragms may be of equal area, the sleeve valve being arranged, as it moves from one controlling position to the other, to subject the outer faces of the pistons or diaphragms alternately to pressure and exhaust.

The actuator may be coupled to the pilot valve, so as to reciprocate it to and fro in relation to the sleeve valve. Alternatively the pilot valvev may be fixed and the sleeve valve housed in a bore in the actuator and caused, byl the actuator, to travel in relation to the Xed pilot valve.

In all cases reversal of the pressure diiference across the actuator is effected purely by relative sliding movement of the sleeve valve and pilot valve. It is preferred to arrange for the pilot valve to close the exhaust connection to that end of the sleeve valve which is connected to exhaust prior to opening the pressure connection to that end of the sleeve valve so that as explained later, the

maximum amount of pressure is then available to move the sleeve valve to its other controlling position.

The usual method of regulating the number of strokes per minute performed by a hydraulic motor is to adjust the supply pressure to the motor according to requirements. if a very low speed of reciprocation is required the supply pressure must be low. This would reduce the pressure available to act on the end of the sleeve valve with the result that its action would be unreliable. The invention accordingly provides, for the purpose of regulating the speed of the motor, an adjustable flow regulating device in one or more of the conduits, controlled by the sleeve valve, for establishing the reversible pressure difference across the actuator. This permits of the desired regulation in the speed of the motor, while nevertheless allowing the full supply pressure and ow to be available to move the sleeve valve, thus changing the sleeve valve over quickly with no dwell of the motor at the end of its stroke. The sleeve valve being mounted externally to the pilot valve has a large surface area at its end, and this, in conjunction with the full supply pressure, generates a powerful force on the end of the sliding sleeve valve, and therefore reduces the possibility of the sleeve valve sticking through foreign matter being present.

Somealternative forms of hydraulic motor according to the invention will now be described in detail, by'way of example, with reference to the accompanying drawings, in which:

Figure l is a longitudinal section through the first form of hydraulic motor, showing the motor coupled to a shower pipe and in the mid-stroke position when its actuator is moving to the left;

Figure 2 is a view of the left hand end of Figure l, showing the position of the parts just before thecompletion of the left hand stroke;

Figure 3 is a view similar to Figure 2, showing the position of the parts after the sleeve valve has moved, from the position of Figure 2, to its right hand controlling position;

Figure 4 is a view similar to Figure 2, showing the position of the parts just before the completion of the right hand stroke;

Figure 5 is a longitudinal section through an alternative form of hydraulic motor for actuating a shower pipe;

Figure 6 is a longitudinal section through a third form of hydraulic motor, showing the same applied for actuating a doctor; and

Figure 7 is a longitudinal section through a fourth form of hydraulic motor, also designed for actuating a doctor.

Like reference numerals indicate like parts throughout the figures. v

The hydraulic motor shown in Figures 1 4 is designed to operate a shower pipe of the ball jet type. The casing of the motor comprises ve portions 10, 11, 12, 13, 14, united by bolts 15, 16, 17. The right hand portion l of the casing is joined, by'bolts 18, to a sleeve 19 supporting a horizontal shower pipe 20. The casing is closed at its left hand end by a cover 58, attached thereto by bolts S9, and at its right hand end to the interior of the shower pipe 20. The actuator of the motor is constituted by a pair of diaphragms 21, 22, clamped between the portions of the casing as shown and supporting a cross head 23. A bolt 24 connects the cross head 23 to an extension 27, and the head 25 of the bolt constitutes a coupling for connecting the cross head to the stem of a pilot valve 26, in such fashion that the pilot valve 26 isconstrained to reciprocate with the cross head 23 while being free to rotate in relation thereto. The extension 27 of the cross head is coupled, by a coupling 28, to a reciprocating pipe 29 mounted coaxially within the shower pipe 20. The pipe 29 is therefore constrained to reciprocate' with the cross head 23 and Carries a., number ofA steadies.. Qi triangular Section, one of which is shown at 30.

Water under pressure is admitted to the portion 14 o the casing, and thence to the interior of the shower pipe 2li, through an inlet 35. The shower pipe has a number of nozzle sockets 31, each containing a ball 32, carrying a hollow stem 33 which projects into and lits closely into a hole in the reciprocating pipe 29 and feeds water to the interior of the ball 32. The balls 32', each of which has a narrow axial jet 34 in it, are thus oscillated to and fro in the nozzle sockets 31 by the pipe 29, to distribute the spray of water. It will be noted that the effective area of the diaphragm 21 is less than that of the diaphragm 22. The right hand face of the diaphragm 2l is always subject to the pressure of the water entering the inlet 35. The larger area of the left hand face of the diaphragm 22, which is preferably more than twice the area of the diaphragm 21 subject to pressure, is subjected alternately to pressure and exhaust, according to the position of a sleeve valve 36 mounted to slide on, and also free to rotate on, the pilot valve 26.

The sleeve valve 36 has three circumferential grooves 37, 38, 39. The central groove 38 communicates, in all relative positions of the sleeve valve 36 and pilot valve 26, with a pressure supply pipe 41, leading from the space 42 open to the inlet 35, and also, via holes 40, with a central waisted portion 43 of the pilot valve, which is of the piston type. The two end grooves 37, 39 are always connected by ports 44, 45 and a passage 46 in the portion of the casing to an exhaust outlet 47. A port 4S in the casing is brought alternatively into register with the central groove 38 and the end groove 39 of the sleeve valve 36 according to the controlling position occupied by the latter. This port 48 communicates, via a conduit 49 containing an adjustable flow regulating needle valve 50, with the left hand face of the diaphragm 22. The needle valve 50 is screwed into the casing and, after removal of a cap 51, can be screwed up or down to regulate the flow. The sleeve valve 36 has in it two axial bores 52, 53, open one to each end of the sleeve valve, which terminate respectively in ports 54, 55 controlled by the pilot valve. The end grooves 37, 39 of the sleeve valve communicate respectively with throughgoing radial holes 56, 57 in the sleeve valve, one of which is closed by the pilot valve and the other open.

When the diaphragms 21, 22 and pilot valve 26 are moving to the left, as shown in Figure l, the sleeve valve 36 is in its left hand controlling position, the right hand end groove 39 of the sleeve valve is in communication with the port 48 leading to the diaphragm 22, the radial hole 57 communicating with the end groove 39 is sealed by the pilot valve 26 and the right hand port 55 in the sleeve valve 36 is opened to the waisted portion 43 of the pilot valve and therefore to pressure. Pressure therefore acts on the right hand end of the sleeve valve, and the left hand end of the sleeve valve is open to exhaust through the left hand radial hole 56.

As the pilot valve 26 approaches the limit of its travel to the left, it seals off the left hand radial hole 56 and the right hand port 55, as shown in Figure 2. Soon afterwards it opens the left hand port 54 to its waisted portion 43 and therefore to pressure, and opens the right hand radial hole 57. The pressure and exhaust connections to the ends of the sleeve valve 36 are thus reversed and the sleeve valve moves to its right hand controlling position, shown in Figures 3 and 4, in which the port 4S for supplying liquid to the diaphragm 22 is in register with its central groove 38 and therefore subject to pressure. The diaphragms 21, 22 and pilot valve 26 therefore move to the right, as shown in Figure 3. Shortly before they reach their right hand end position, the pilot valve 26 closes the radial hole 57 and the port 54 as shown in Figure 4. Soon afterwards the pilot valve 26 moves on to open the port 55 and the radial'hole 56, so once more reversing thepressure and exhaust connections to the ends of the sleeve valve 36. This then travels to its left hand cnntrolling. position, shown in Figures 1 and 2, to initiate a further movement of the diaphragms and pilot valve to the left.

It will be noted that, as the pilot valve 26 nears the end of its stroke, it closes the exhaust outlet 56 or 57 from that end of the sleeve valve 36 which is connected to exhaust before it opens the port 54 or 55 by which pressure is supplied to that end of the sleeve valve. This has the effect of generating, due to the ratio between the area of the diaphragm subjected to pressure and the area of the end of the pilot valve, a pressure on the end of the sleeve valve much greater than the supply pressure, and so provides a more powerful force to start the movement of the sleeve valve should this valve be stickingf due to a deposit of foreign matter.

An important feature is that the sleeve valve 36 moves in the opposite direction to the pilot valve 26, and so the port 54 or 55 which is about to act as the pressure port is uncovered by the differential movement at a speed greater than that at which the pilot valve is moving; this prevents wire drawing and damage to the port faces.

The arrangement of the ports is such that no unbalanced radial pressure is applied to either valve (except to the sleeve valve during the brief changing-over period) with the result that sliding friction is kept to the very minimum. Also, as both valves 26, 36 are free to rotate and, in fact, do so while the mechanism is in operation, the amount of wear is negligible.

At the right hand end, dead centering is avoided, as when the exhaust port 57 (Figure 4) is closed by the pilot valve, the port 48 is still in full engagement with the groove 38 in the sleeve and groove 43 of the pilot valve is just barely out of engagement with port 5S of the sleeve and fully out of engagement with port 54 of the sleeve. Under these circumstances, any build-up of pressure between the pilot valve and member 11, occasioned by rightward advance of the diaphragm 22 will shift the sleeve to the left, while the pilot valve makes an equivalent movement to the right. This engages port 55 of the sleeve with groove 43 of the pilot, and via ports and groove 38 of the sleeve delivers line pressure to the space between the pilot and member 11. This pressure completes the shift of the sleeve to its leftward position opening diaphragm 22 and the left ends of the sleeve and pilot to exhaust.

The arrangement of the valves is such that the motor is always self-starting should the supply be stopped when either of the valves is in the middle, end, or at any position of its stroke. There is no dead center trouble.

The valve gear is of simple mechanical design, easily manufactured and with Very few surfaces liable to wear. It constitutes an external unit which can easily be removed from the shower pipe and exchanged or taken apart, should large particles of foreign matter cause the sleeve valve to stick. A tine lter to handle the oscillator liquid only, additional to any filter in the main supply, can be fittedA in the supply pipe 41 to the valve gear. The speed regulating device is external and easily adjusted while the mechanism is in operation.

Figure 5 shows an alternative form of hydraulic motor, also intended for operating a shower pipe (not shown) which is fitted to the right hand portion 14 of the casing in similar fashion to the shower pipe shown in Figure 1, the oscillating pipe being connected to the extension 27. The motor shown in Figure 5 is similar in principle to that shown in Figures 1 4, but differs in that the valve mechanism is mounted between the two diaphragms 21, 22, which are joined by a cylindrical cross head 60 within which the pilot valve 26 and sleeve valve 36 are disposed. The pilot valve 26 has a piston rod 61 projecting through the diaphragm 22 and engaged at its left hand end by a lip 62 on the cover 58 which holds the valve 26 against reciprocating movement but allows it to rotate. A pressure conduit 63 extends from the space 42 through the4 diaphragm 21 and cross head 60, and communicates via a port 18, with the central groove 38 in the sleeve valve 36. In this arrangement the sleeve valve 36 is pushed to and fro in relation to the fixed pilot valve 26 by the abutment against it of the ends 84 of the cylindrical cavity in the cross head 60, and the port 48 leading to the conduit 49 containing the ow regulating valve 50 cooperates alternatively with the grooves 39, 38 in the sleeve valve. The conduit 49 leads through the diaphragm 22 to the space 65 at the left hand side thereof. When the diaphragms 21, 22 are travelling to the left as shown in Figure 5, the sleeve valve 36 occupies its right hand controlling position in relation to the diaphragms and travels to the right with the diaphragms. Shortly before the end of the movement to the right of the sleeve valve and diaphragms, the ports S4, 57 will be closed by the pilot valve 26. Shortly thereafter, the pilot valve opens the ports 55, 56 with the result that pressure is applied to the left hand end of the sleeve valve, its right hand end being simultaneously connected to exhaust. The sleeve valve therefore runs the diaphragms and moves to its right hand controlling position.

As will readily be seen, the space 65 is then connected to exhaust, due to the port 48 being brought into register with the groove 39, with the result that the diaphragms and sleeve valve will move to the left. Shortly before the end of the left hand stroke, the piston valve will, as before, reverse the pressure and exhaust connections to the ends of the sleeve valve, and the latter will overrun the diaphragms and move once more to its left hand controlling position, supplying pressure to the space 65 and causing the diaphragms to move to the right again.

The arrangement of Figure 5 shares the advantages of that of Figures 1-4, viz., the valves 26, 36 are freely rotatable, the pilot valve will shut off the port, 56 or 57, communicating with the end of the sleeve valve subjected to exhaust before it opens the port, 54 or 55, for supplying pressure to that end of the sleeve valve, and the sleeve valve will move very rapidly in relation to the pilot valve when moving from one controlling position to the other. Prior to the change over, the moving sleeve valve will move relatively to the fixed pilot valve at the same speed as the moving pilot valve moves in relation to the fixed sleeve valve in the case of Figures l-4, and during the change over the sleeve valve will move at an accelerated speed in relation to the fixed pilot valve in response to the reversal of the pressure difference across it.

As an alternative to the use of diaphragms, pistons of dissimilar area may be attached to opposite ends of the cylinder surrounding the valve gear. Such an arrangement is shown in Figure 6, which Shows a hydraulic motor for actuating a doctor in a paper making machine, or some other device external to the motor. The motor of Figure 6 differs from that of Figure 5 in that the diaphragms 21, 22 are replaced by pistons 71, 72 which are shown moving to the right in Figure 6. therefore, that explanation of the operation of the motor of Figure 6 is unnecessary. The space 42 to which the outer face of the smaller piston 71 is exposed is subjected to the pressure of oil entering the inlet 35, while the space 65 to which the outer face of the larger piston 72 is exposed is alternately connected to pressure and exhaust according to the controlling position assumed by the sleeve valve.

In the case of Figure 6 the casing is constituted by a single member 10, with the cover 58 attached to its right hand end. The piston rod 61 extends through the right hand piston 71 and is anchored at 62 to the cover 58. The left hand end of the casing is closed by a cover 66 fixed to it by bolts 73. In use of the motor, the cover 66 is attached by bolts 67 to the face of the paper making machine. A piston rod 68, connected to the piston 72, extends through the cover 66 and an extension 69 thereof is iixed to the journal of the doctor. A gland 70 is provided for preventing leakage of oil from the casing past the piston rod 68.

In Figure 7 is shown an alternative form of hydraulic It is believed,-

motor for actuating a doctor or other apparatus external to the motor. .It is generally similar to the motor of Figure 6, except that the pistons 171, 172 are of equal area. The ports controlled by the valve mechanism are accordingly modified so that in one controlling position of the sleeve valve pressure is supplied to the outer face of one piston and the outer face of the other piston is connected to exhaust while, when the sleeve valve moves to its other controlling position, these pressure and exhaust connections are reversed. This is achieved as follows:

Oil under pressure is supplied through a duct 74 in the piston rod 68 and thence to a passage 75 in the cylindrical cross head '60. The passage 75 communicates, via a port 76, with the groove 38 in the vsleeve valve, and, in all positions of the sleeve valve, pressure is thence supplied to the waisted portion 43 of the pilot valve 26 by one or other of the ports 40.

A port 77 communicates, via a passage 78, with the left hand of the cylindrical cavity in the casing 10 and a port 79 communicates, via a passage 80, with the right hand end of the cylindrical cavity. When the sleeve valve 36 occupies its left hand controlling position, as shown in Figure 7, the port 77 is open to the groove 38 and therefore to pressure and the port 79 is open to the groove 39 and therefore to exhaust. Consequently the piston 172 is subjected to pressure and the piston 171 to exhaust, and the pistons and piston rod 68 move to the right, taking the sleeve valve with them. Shortly before the end of the stroke, the pressure and exhaust connections to the sleeve valve 36 are reversed by the pilot valve 26, as in the case of the arrangements already described, and the sleeve valve travels to its right hand controlling position. The port 77 is then connected to the groove 37, and therefore to exhaust, and the port 79 to the groove 38 and therefore to pressure. Consequently the pistons 171, 172 travel to the left.

A ilow regulating device, similar to that shown in Figures 1-6, but not shown in Figure 7, is provided in each of the conduits 78, 80.

I claim:

l. In a hydraulic motor: a member reciprocable by the application of a pressure differential alternately on opposite sides thereof; a valve mechanism comprising a casing having inlet and discharge ports, a sleeve valve reciprocable within said casing, a pilot valve reciprocable within said sleeve valve, said sleeve valve having means coacting with the inlet and discharge ports of said casing for alternating said pressure differential between opposite sides of said member, said sleeve valve having two pairs of inlet and discharge ports coacting with said pilot valve for connecting opposite ends of the interior of said sleeve valve alternately with the inlet and discharge ports of said casing; means producing reciprocation of said pilot valve within said sleeve valve as a concomitant of the reciprocation of said member, said pilot valve having spaced lugs fitting the interior of said sleeve valve, said lugs being connected by a portion of reduced diameter, the length of said lugs and the spacing of each pair of ports in Said sleeve valve being so proportioned that during advance of said pilot valve within said sleeve valve in either direction, the discharge port of the pair of ports toward which the lug advances, is closed before the inlet port of such pair is opened, whereby continued advance of said pilot valve moves the sleeve valve, within said casing in a direction opposite to that of the advance of the pilot valve.

2. In a hydraulic motor: a member reciprocable by the application of a pressure differential alternately on opposite sides thereof; a valve mechanism comprising a casing having inlet and discharge ports, a sleeve valvev reciprocable within said casing, a pilot valve reciprocable within said sleeve valve, said sleeve valve having means coacting with the inlet and discharge ports of said casing for alternating said pressure differential between opposite wsu..

sides of said member, saidv sleeve valve having two pairs of inlet and discharge ports coacting with said pilot valve for connecting opposite ends of'` the interior of said sleeve valve alternately with the inlet and discharge ports of said casing; means producing reciprocation of said pilot valve within said sleeve valve in synchronism with the reciprocation of said member, said pilot valve having spaced lugs fitting the interior of said sleeve valve, said lugs being connected by a portion of reduced diameter, the length of said lugs and the spacing of each pair of ports in Said sleeve valve being so proportioned that during advance of said pilot valve within said sleeve valve in either direction, the discharge port of the pair of ports toward which the lug advances, is closed before the inlet port of such pair is opened, whereby continued advance of said pilot valve moves the sleeve valve, within said casing in a direction opposite to that of the advance of the pilot valve. t

References Cited in the le of this patent UNITED STATES PATENTS 825,950 Weir July 17, 1906 923,486 Bowen June 1, 1909 lo 927,560 Lewis July 13, 1909 1,779,586 Chalker et al Oct. 28, 1930 1,938,021 Hobson Dec. 5, 1933 2,080,839 Stone May 18, 1937 2,355,434 Harter Aug. 8, 1944 15 2,432,305 Geiger Dec. 9, 1947 

